The present invention relates to a tire with radial carcass reinforcement intended to support heavy loads and inflated to relatively high pressures for high speed use, in particular an airplane tire.
The radial carcass reinforcements of such tires generally comprise several plies of textile cords, which are anchored in each bead to at least one bead wire and generally have a single bead wire. The reinforcing elements of these reinforcements are wound around said bead wire from the inside to the outside, forming turn-ups, the respective ends of which are spaced radially from the axis of rotation of the tire. The severe conditions under which airplane tires are used are such that the life of the beads is short, particularly in the area of the turn-ups of the carcass reinforcement.
A substantial improvement in performance is obtained by the separating of the plies of the carcass reinforcement into two groups. The first group comprises the plies of the carcass reinforcement which are axially towards the inside in the region of the beads, these plies being then wound around a bead wire in each bead from the inside to the outside of the tire. The second group is formed of at least one axially outer ply in the region of the beads, which ply is generally wound around the bead wire from the outside to the inside of the tire. Such arrangements are known; for instance, in U.S. Pat. No. 4,244,414.
The life of beads formed in this manner can be improved by the presence in each bead of an additional reinforcement ply, wound around the bead wire and thus forming an axially outer leg and an axially inner leg, said reinforcement ply, also known as an inner flipper, being the ply closest to the rubber filler, radially above the anchoring bead wire. A tire structure of this type is shown in U.S. Pat. No. 5,285,835. In U.S. Pat. No. 5,769,982, the life of the beads of airplane tires can be further improved, particularly when they are subjected to heavy overloads which can result in a crushing of the order of 50% and more of their height, by having the arrangement of the ends of the turned-up portions or turn-ups of the inner carcass plies and the ends of the legs of the inner flipper with respect to the radial position of the radially upper end of the rubber filler located above the anchoring bead wire and the filler.
In accordance with that invention, an airplane tire, inflated to a high pressure, having a tread, a crown reinforcement, and a radial carcass reinforcement comprising at least two axially inner plies of textile cords wound around a bead wire in each bead from the inside to the outside forming turn-ups and at least one axially outer ply of textile cords superimposed on the inner plies below the crown reinforcement and along the turn-ups in said beads, said bead wire being radially surmounted by a filler of vulcanized rubber mix, having the shape substantially of a triangle, the apex of which radially furthest from the axis of rotation is at a distance D from a straight line parallel to said axis, passing through the geometrical center of the circle circumscribed on the cross-section of the anchoring bead wire, known as the reference line, and also comprising at least one inner flipper wound around the bead wire to form an axially inner leg and an axially outer leg which are axially adjacent to the filler above the bead wire, characterized by the fact that the end of the axially outer leg of the inner flipper is located at a radial distance LE from the reference line such that LE is between 0.40 D and 0.80 D; the end of the turn-up of the inner carcass ply arranged axially furthest to the inside is located at a distance HA from the reference line such that HA is between 0.15 D and 0.50 D, and by the fact that the ends respectively of the inner leg of the inner flipper and of the turn-ups of the inner carcass ply or plies which are axially furthest to the outside.
While this construction is durable, it limits the number of carcass plies that can be provided in the bead area and the extended length of the flipper means that the outer plies being turned down around the bead and the inner plies are spaced from the natural ply path of the tire in the region of the flipper. This spacing, while believed desirable, results in one less ply being available in the structure and in the case of very large aircraft the tire structure ideally may require the use of another ply which is effectively precluded by the use of the extend length flipper.
It is an object of the present invention to provide a lightweight efficient tire structure having superb durability.
It is a further object of the present invention to provide an improved bead structure wherein the use of inside turn-up plies and outside turndown plies is optimized by the placing of the plies close to the natural ply path.
A pneumatic tire for use on aircraft has a nominal bead diameter NBD, a crown reinforcement, and a radial carcass reinforcement having at least two axially inner plies of textile cord wound around a pair of bead cores, the bead cores having a maximum radial height Bh. Each inside ply is wound around the bead from inside to outside forming outside turn-ups. At least one axially outer ply of textile cords extends from bead to bead along the turn-ups of the inner plies. Each bead has an elastomeric filler of substantially triangular shape, the apex of the filler is located above the bead core extending to an apex A as measured from a line YYxe2x80x2 parallel to the axis of the tire and passing through the location of the nominal bead diameter or as measured from a reference line XXxe2x80x2 parallel to the axis of rotation and passing through the geometric center of the bead core.
The tire has a flipper wound around the bead core to form an axially inner leg and an axially outer leg, the axially inner leg is located at a radial distance Li from the reference line YYxe2x80x2 or XXxe2x80x2 and the axially outer leg is located a radial distance Le from the reference line YYxe2x80x2 or XXxe2x80x2. The flipper is oriented where Bh less than LE less than 0.7D and Bh less than LI less than 0.7D and at least one axially inner ply has turn-ups when the tire has two or more axially inner plies, at least one turn-up is radially above the apex location A and at least one turn-up is below the location A.
The ends of the axially outer leg of the flipper and the ends of the turn-ups of the inner plies are radially staggered.
xe2x80x9cApexxe2x80x9d means a non-reinforced elastomer positioned radially above a bead core.
xe2x80x9cAspect ratioxe2x80x9d of the tire means the ratio of its section height (SH) to its section width (SW) multiplied by 100% for expression as percentage.
xe2x80x9cAxialxe2x80x9d and xe2x80x9caxiallyxe2x80x9d means lines or directions that are parallel to the axis of rotation of the tire.
xe2x80x9cBeadxe2x80x9d means that part of the tire comprising an annular tensile member wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes, toe guards and chafers, to fit the design rim.
xe2x80x9cBelt or breaker reinforcing structurexe2x80x9d means at least two layers of plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having both left and right cord angles in the range from 17xc2x0 to 33xc2x0 with respect to the equatorial plane of the tire.
xe2x80x9cBias ply tirexe2x80x9d means a tire having a carcass with reinforcing cords in the carcass ply extending diagonally across the tire from bead core to bead core at about a 25xc2x0-50xc2x0 angle with respect to the equatorial plane of the tire. Cords run at opposite angles in alternate layers.
xe2x80x9cCarcassxe2x80x9d means the tire structure apart form the belt structure, tread, under tread, and sidewall rubber over the plies, but including the beads.
xe2x80x9cCircumferentialxe2x80x9d means lines or direction extending along the perimeter of the surface of the annular tread perpendicular to the axial direction.
xe2x80x9cChafersxe2x80x9d refers to narrow strips of material placed around the outside of the bead to protect cord plies from the rim, distribute flexing above the rim, and to seal the tire.
xe2x80x9cChippersxe2x80x9d means a reinforcement structure located in the bead portion of the tire.
xe2x80x9cCordxe2x80x9d means one of the reinforcement strands of which the plies in the tire are comprised.
xe2x80x9cEquatorial plane (EP)xe2x80x9d means the plane perpendicular to the tire""s axis of rotation and passing through the center of its tread.
xe2x80x9cFlipperxe2x80x9d means a reinforced fabric wrapped about the bead core.
xe2x80x9cFootprintxe2x80x9d means the contact patch are area of the tire tread with a flat surface at zero speed and under normal load and pressure.
xe2x80x9cInnerlinerxe2x80x9d means the layer or layers of elastomer or other material that form the inside surface of a tubeless tire and that contain the inflating fluid within the tire.
xe2x80x9cNet-to-gross ratioxe2x80x9d means the ratio of the tire tread rubber that makes contact with the road surface while in the footprint, divided by the area of the tread in the footprint including non-contacting portions such as grooves.
xe2x80x9cNormal inflation pressurexe2x80x9d refers to the specific design inflation pressure and load assigned by the appropriate standards organization for the service condition for the tire.
xe2x80x9cPlyxe2x80x9d means a continuous layer of rubber-coated parallel cords.
xe2x80x9cRadialxe2x80x9d and xe2x80x9cradiallyxe2x80x9d means directions radially toward or away from the axis of rotation of the tire.
xe2x80x9cRadial-ply tirexe2x80x9d means a belted or circumferentially-restricted pneumatic tire in which the ply cords which extend from bead to bead are laid at cord angles between 65xc2x0 and 90xc2x0 with respect to the equatorial plane of the tire.
xe2x80x9cSection height (SH)xe2x80x9d means the radial distance from the nominal rim diameter of the tire at its equatorial plane.